In recent years, image guided surgery has become more and more common, in part because of the ability of a surgeon to view internal images of a patient's anatomy and pre-plan a medical operation. In this way, pre-acquired images of the anatomical body are used to plan the course of the medical procedure, whether the medical procedure is diagnostic, therapeutic or surgical in nature. The pre-acquired images can also be used, to some extent, during the medical procedure for orientation of the surgeon with respect to the internal anatomy of the patient.
The images of a patient's external or internal anatomy used in image guided surgery can be generated by a number of means, including computerized tomography (CT), magnetic resonance imaging (MRI), video, ultrasound and X-rays. Images may also be captured using angiography, single photon emission computer tomography and positron emission tomography (PET). In all cases, at least two, and generally more than two, images of the patient's internal anatomy are generated. The images are captured such that the relative position of the images is known. The images, along with information indicating the relative position of the images, can then be stored in a data-base to essentially create a data-base body comprised of the pre-acquired images and corresponding to the anatomical body of the patient at the time the images were captured.
This data-base body of images can be used for a number of purposes, including diagnosis or to pre-plan the medical procedure. In addition, it is known in the art to process this data-base body of pre-acquired images in order to produce images of various views, as well as three-dimensional images, based on the relative spatial relationship of the pre-acquired images within the internal anatomical structure of the patient.
Surgeons can pre-plan the course of a medical procedure by marking, either manually or electronically, on the data-base body of pre-acquired images the course of the medical procedure. The markings can indicate areas of interest, objects of concern, as well as proposed cuts or drilling locations and orientations, and locations which must be irradiated with specific types of radiation for diagnostic or therapeutic procedures. During the medical procedure, the surgeon can then refer to the markings on the images to assist in performing the procedure.
Furthermore, the prior art imaging devices can project a representation of the instrument or tool being used by the surgeon onto the pre-acquired images during a medical procedure. The representation corresponds to the position of the actual instrument or tool with respect to the patient. By viewing the position of the representation of the instrument or tool with respect to the data-base body of pre-acquired images, the surgeon can extrapolate the position of the actual probe or instrument with respect to the internal anatomy of the patient. In addition, the surgeon can simultaneously follow the pre-planned markings on the pre-acquired images.
However, the prior art imaging devices and methods suffer from the disadvantage that the surgeon's attention is no longer directed solely toward the patient during the surgery, but rather is also directed toward the pre-acquired images, the pre-planned markings and the representations of the probes and instruments on the images. In other words, during image guided surgery, the surgeon's attention is split between the patient and the data-base image of the patient. This is often disconcerting for surgeons, and in particular surgeons who are unfamiliar with image guided surgery, because their attention is no longer solely directed toward the patient, as is the case with other types of surgery. Rather, the surgeons must view the image of the patient and the representation of the probes and instruments with respect to the data-base image while manipulating the actual probes and instruments within the patient. This can adversely affect the surgeon's hand-eye co-ordination and could result in the surgeon becoming disoriented.
Also, because the attention of surgeons during image guided surgery is split between the patient and the image of the patient, there is a risk that a surgeon will not notice that the surgeon has stuck, or will strike, a "critical structure" within the patient. Critical structures include an organ or blood vessel, which, if struck, can critically or severely damage the patient. This is compounded by the fact that several imaging techniques do not provide detailed images of critical structures, such as organs or blood vessels, and a surgeon may not immediately see them if the surgeon's attention is directed towards the pre-acquired images rather than at the patient.
A further disadvantage of the prior art imaging systems is that all pre-planned markings made by the surgeon are located on the pre-acquired images. Accordingly, in order to use the pre-planned markings, the surgeon must constantly refer to the images and orient the images and pre-planned markings to the anatomical body during the course of the medical procedure.